A method for uniformly coating the surface of an impeller with a drag reduction material comprises the following steps: forming a runner model; manufacturing a runner mold core; and at last, placing the mold core painted with a release agent in a runner of the impeller, performing positioning between an upper cover plate and the mold core, a lower cover plate and the mold core, a working face andthe mold core, and a working back side and the mold core of the impeller according to the thickness of the drag reduction material for coating to reserve gaps, closing a water outlet of the impeller by an adhesive tape painted with the release agent, pouring the drag reduction material from a water inlet till the gaps are fully filled, and drawing out the hard mold core after finish of curing of the drag reduction material on the inner surface of the runner of the impeller to finish coating. The size of the runner model is uniformly reduced to obtain the mold core, and all parts in the runnercan be uniformly covered with the drag reduction coatings in the coating process. Meanwhile, a prepolymer and a curing agent of the drag reduction material are uniformly mixed in advance and vacuumized, and then coating is performed. Compared with spray-coating equipment, the provided method has the advantages that the coatings are prevented from bubbles, nonuniform mixing is avoided, the abrasionresistance of the drag reduction coatings is improved, and a better binding effect is achieved.